February 2013

When studying the requirements for CNS re-activation of CD81 T cells in (CD41 T cells-induced) experimental autoimmune encephalomyelitis or EAE, Ji and colleagues discovered that myelin basic protein (MBP) was presented to the infiltrating CD81 T cells by CD11b1 “Tip-dendritic cells” (tumornecrosis factor inducible nitric oxide synthase producing DCs), derived from monocytes that infiltrated the inflamed CNS and didn’t traffic to draining lymph nodes. Interestingly, during the course of their investigation, the authors also detected MBP– MHC complexes on oligodendrocytes (but not astrocytes or endothelial cells) of mice with EAE, and these cells triggered exvivo the production of IFN-c by T cells. Thus, under inflammatory conditions oligodendrocytes could be direct lytic targets of MBP-specific CD81 T cells and become a source of myelin debris or exosomes that will propagate the inflammatory response, including determinant spreading (Nat Immuno 2013; doi:10.1038/ni.2513).